A gas turbine includes a number of stages with buckets extending outwardly from a supporting rotor disk. Each bucket includes an airfoil over which combustion gases flow. The airflow must be cooled to withstand the high temperatures produced by the combustion gases. Insufficient cooling may result in undue stress on the airfoil and may lead or contribute to fatigue and/or damage. The airfoil thus is generally hollow with one or more internal cooling flow channels. The internal cooling flow channels may be provided with a cooling air bleed from the compressor or elsewhere. Convective heat transfer may be enhanced between the cooling flow and the internal metal surfaces of the airfoil by the use of pin-fin arrays, turbulators, and the like. The pin-fin arrays or the turbulators create a disruption in a surrounding boundary layer so as to increase heat transfer.
An airfoil generally has a single cooling flow feed leading to a pin array and multiple outlets. Such a configuration, however, typically results in a flow through the pin array that is at an angle relative to the outlets. This angled flow may lead to a less effective heat transfer therein. Flow straighteners may be used but such add space and complexity to the pin array region.
There is thus a desire for an airfoil with an improved internal cooling flow scheme with a pin-fin array. Such an improved cooling flow scheme may provide a pin-fin array for more effective heat transfer, better flow control, and lower manufacturing costs.